Ancient DNA reveals how wheat came to prehistoric Britain

February 26, 2015This article courtesy of Nature News.

Finding suggests trade between British hunter-gatherers and European farmers.

Hunter-gatherers in ancient Britain may have imported cereals from Europe long before
they turned to farming. Ancient DNA recovered from soil submerged beneath the English
Channel suggests that wheat appeared in Britain some 2,000 years before Neolithic
farmers began cultivating cereal grains there. But not all archaeologists are convinced
by the new findings, which are reported in Science1.

The Mesolithic-to-Neolithic transition, when modern humans began to settle and grow
food, marks a key step in the evolution of civilization and technology. In Europe,
agriculture slowly spread from ancient Anatolia (modern-day Turkey), where domesticated
plants including wheat were first farmed about 10,000 years ago, through the Mediterranean
and central Europe. Archaeologists believe that farming did not reach the British
Isles until about 6,000 years ago.

But wheat may not have been completely absent in pre-Neolithic Britain. At Bouldnor
Cliff, a prehistoric site that lies just off the Isle of Wight and which is submerged
under 11 metres of water, scientists have recovered DNA of wheat (Triticum) that matches Near Eastern strains.

The team found no cereal-plant pollen or any other archaeological evidence to suggest
that wheat was grown at the site. The grain — or flour, from which the inhabitants
of Bouldnor Cliff may have made basic dough — must have come from a distant place,
perhaps from the Balkans or the south of France, which Neolithic farmers had already
reached, the researchers conclude.

Prehistoric markets

“Mesolithic Britain was not isolated from culturally more advanced mainland Europe
as has been argued,” says Robin Allaby, an anthropologist and plant geneticist at
the University of Warwick in Coventry, UK, who was involved in the study. “There was
apparently some level of interaction, by trade or warfare or both. In any case, the
peoples who frequented Bouldnor Cliff must have been aware of products and techniques
developed in distant parts of Europe, and they seem to have imported goods and ideas
to Britain.”

A possible land connection between Britain and Europe at the end of the last ice age
might have made trading easier. Ten thousand years ago, rising sea levels — a result
of melting glaciers — had already created the English Channel. But the study authors'
reconstruction of coastlines, based on the age of marine sediments from the British
east coast, supports the possibility that two small points of contact with northern
France and the Netherlands still existed until about 7,800 years ago. But a land connection
is not even necessary for the early arrival of wheat on the British Isles, says Allaby.
“Peoples on both sides of the Channel would have been able at the time to traverse
the shallow seas with boats,” he says.

Indeed, Bouldnor Cliff was the site of a Mesolithic boat-building yard. As the sea
level rose further, the land there turned into a peat bog before it was inundated
and eventually abandoned. But because the peat seals the ancient land surface, the
former terrestrial soil and sedimentary DNA it includes are exceptionally well preserved.
Preserved plant pollen in the sediment hints at an ancient landscape populated by
oak, poplar and apple trees. DNA analysis and fossils suggest that dogs, wolves, deer
and aurochs (an extinct large, wild ox) had roamed the land.

The researchers took pains to prevent other DNA from contaminating their samples.
But genetic analysis is a relatively new addition to archaeologists’ toolbox, and
some remain sceptical.

“Archaeology constantly throws up surprises, but these findings look puzzling to me,”
says Peter Rowley-Conwy, an archaeologist at Durham University, UK. He points out
that farming had hardly spread north of the Danube 8,000 years ago. “This seems too
far for hunter-gatherer networks to extend,” he says. “Artefacts such as flint blades
and arrowheads that appeared around that time from Portugal to the Urals never made
it to Britain — it’s hard to believe that wheat should.”

The findings need to be confirmed in the greater context of existing archaeological
research, he says. But Mesolithic settlements that could shed light on the issue are
hard to find in mainland Britain. To understand how and when Neolithic culture arrived,
says Allaby, "the answer probably lies under the sea".